1. Field of the Invention
This invention relates to a multichamber cuvette and its use and relates more particularly to such cuvette which, while not limited thereto, is especially useful in analysis by optical density in an automated manner of a constituent of body fluids such as blood or urine for example.
2. Prior Art
Brown et al. U.S. Pat. No. 3,691,017, Mailen U.S. Pat. No. 3,795,451 and Rosse et al. U.S. Pat. No. 3,718,439 are typical of the prior art. Brown et al disclosed a multichamber cuvette for analysis of a constituent of interest in body fluids by an optical density determination in an automated manner. It was disclosed by Brown et al that a reaction may be measured in the cuvette at one point in its duration or at its end point or a reaction in the cuvette may be temperature-and-time dependent and of the type, measured over a period of time, indicating the quantity of the constituent of interest by the rate of the reaction. In accordance with Brown et al., in such kinetic or rate reaction analyses of an enzyme, a trigger or key reactant component, initially located in a first chamber in restricted communication with a second chamber, was of a substrate of an enzymatically catalyzed reaction with a component in the second chamber, and wherein, after a solvent medium had been introduced in the chambers to reconstitute the reagents previously in lyophilized form, a substance (liquid sample) comprising the catalyzing enzyme was introduced into the second chamber prior to forceful injection thereinto of the key substance for the reaction to proceed under temperature-controlled conditions.
The cuvette was found to have many drawbacks in practice adversely affecting analysis among which, of a more serious type, were that the cuvette did not provide a uniformly precise viewing length of the reaction mixture, portions of the minute liquid volumes utilized in the cuvette evaporated to the atmosphere, the reactants were not sufficiently isolated to prevent comingling and contamination was found to exist in the chambers of the cuvette during use. The contamination was with reference to sample carryover, in dispensing using the same probe of one sample utilized in one cuvette, to the next following dispensed sample utilized in another cuvette.
The design of the cell was such that the liquids which required separation prior to intentional mixing in a cuvette were separated primarily only by a restricted passageway formed by two opposing ribs and providing an opening (1.5 mm .times. 2.5 mm) of sufficient size that water flowed therethrough on reconstitution of the lyophilized reagents. The passageway was of an axial length of only the thickness of a relatively thin rib or partial partition, though the last-mentioned patentees taught that the length of the passageway could be extended. Such being the case, the aforementioned reconstituted reagents in the two chambers of the cuvette were in liquid interfacing relation within the cuvette prior to intentional mixing of the reagents for the reaction to proceed under controlled conditions. Statements of the patentee to the contrary notwithstanding, this enabled a small quantity of one of the liquid reagents to migrate into and commence reaction with the other liquid reactants during the period of time when it was desired to maintain the liquids in complete isolation from one another, as during incubation, to prevent their reaction with one another. It was found that migration by diffusion of only 3% of the reconstituted aforementioned trigger or key component in liquid form into the aforementioned second chamber was sufficient to invalidate an analysis. Such migration might be occasioned by jarring the cuvette. Further, in accordance with Brown et al, only a single diluent was used in a single injection to reconstitute the different reagents in both chambers and any buffer substances in a communicating buffer section within the second chamber. This injection was made into the second chamber for partial retention and flow therethrough and the buffer section into the first chamber for retention therein, resulting in a high degree of risk of comingling of the reagents.
In the manufacture of the cuvette, liquid reagents were introduced onto plural surfaces of the cuvette and lyophilized in situ. The design attempted to separate in the cuvette such reagents while in lyophilized form but in fact permitted comingling of such lyophilized reagents in a manner to prejudice analyses. Such lyophilized reagents were later reconstituted by addition of a suitable solvent after assembly of the dual sections in the cuvette body. The chambers were not sealed from the external environment in use, permitting evaporation of a liquid contents. Moreover, as the windowed light path through the cuvette for viewing the reaction therein was provided in part in one of the dual sections and in part in the other, the combined tolerances to which the sections were manufactured resulted in considerable variation in light path length through the reaction, adversely affecting the precision of analysis. Further, the cuvette exhibited poor heat transfer, and was difficult and expensive to manufacture with the packaged reagents.
Rosse et al. U.S. Pat. No. 3,718,439 discloses a hermatically sealed cuvette body defining three reactant-receiving chambers having a fluid communication therebetween and each provided with a pair of optical windows, the windows of the pairs being uniformly spaced.
Mailen U.S. Pat. No. 3,795,451 disclosed a rotor for loading and mixing sample and reagent liquids for use in a photometric analyzer of the rotary sample-analysis cuvette type. Inner and outer concentric arrays of loading cavities were disposed within the rotor on a one-to-one basis centripetal to an array of sample analysis cuvettes. Liquid communication was provided by capillary-sized passageways between the respective sample, reagent and analysis cavities and cuvettes upon rotation of the rotor, while intercontact of the liquids in the respective cavities was prevented under static loading conditions. The aforementioned respective passages between the inner and outer cavities were each provided with an air lock in the form of a bubble trap under static conditions.
The present invention overcomes difficulties with the prior art.